Decoder for decoding still pictures data and data on which data length of still picture data is recorded reproducing apparatus for reproducing recording medium and reproducing method thereof

ABSTRACT

In a picture data reproducing apparatus, a data dropout from a disc such as a CD-DA can be avoided. In a still picture data reproducing apparatus for reproducing a recording medium on which both of still picture data having at least variable data length, and data length information corresponding to the still picture data have been recorded, this reproducing apparatus is characterized by including: a reader for reading out both of the still picture data and the data length information corresponding to the still picture data from the recording medium; a decoder for decoding the still picture data and also the data length information corresponding to the still picture data, which are read out by the reader; a counter for counting a data length of the still picture data decoded by the decoder; a comparator for comparing the data length information decoded by the decoder with the data length counted by the counter; and a controller for making such a judgement that the data is dropped out by way of the comparator when the data length information decoded by the decoder is not coincident with the data length of the still picture data counted by the counter, and for controlling the reader to again read out the same still image data.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reproducing apparatus capable ofreproducing a disc on which still picture (static image) data has beenrecorded.

2. Description of the Related Art

Various disc media such as audio compact discs, i.e., a so-called"read-only disc" have been popularized. As to audio compact discs,digital audio data are recorded on the discs to reproduce music and thelike with high sound qualities. As one sort of such an audio compactdisc (CD-DA), a CD-Graphics (CD-G) in which still image data has beenrecorded within subcode data is known.

Furthermore, such a video CD that not only digital audio data, but alsomoving picture data as well as still picture data have been recorded hasbeen developed as one sort of a so-termed "CD-ROM".

SUMMARY OF THE INVENTION

On the other hand, video CDs are equipped with not only a function tomerely reproduce moving picture data, but also a so-called "playbackcontrol function". That is, a still picture (image) such as a menuscreen is reproduced, and the reproducing operation is carried out in anuser interactive form.

In the above-described playback function, the menu screen recorded asthe still picture data is reproduced, and then the user performs theselection operation in accordance with the content of this menu screen.Then, the data corresponding to the selection tree selected by the useris reproduced. The moving picture data, the still picture data, theaudio data and the like are employed which may be designated as thereproduced selection tree.

In particular, the still image such as the menu screen, and the stillpicture reproduced based on the menu selection are recorded on apredetermined region on a disc as the segment play item, which isindependent from the moving picture data. There are some possibilitiesthat a segment play item may be handled as moving picture data.

On the other hand, when data is read out from a disc, a portion of readdata may be possibly dropped out due to adverse influences bydisturbance such as defects and finger prints.

When the still picture data is reproduced, a great problem may occur ifdata is dropped out during the data reading operation of the disc.

In other words, in the case that the still picture data is reproduced,since the data about one screen which have been once read out from thedisc are continuously outputted for a preselected time period, the dataportion when a portion of the data read from the data is lost would notbe eventually displayed on the screen.

For instance, such a trouble may happen to occur that if a portion of amenu image is lost which is required for user selections, then the usercannot make any menu selection.

To solve the above-described problems, according to the presentinvention, in a reproducing apparatus for reproducing a recording mediumon which both of still picture data having at least variable datalength, and data length information corresponding to the still picturedata have been recorded, this reproducing apparatus is characterized bycomprising:

a reader for reading out both of said still picture data and said datalength information corresponding to the still picture data from therecording medium;

a decoder for decoding the still picture data and also the data lengthinformation corresponding to said still picture data, which are read outby said reader;

a counter for counting a data length of said still picture data decodedby said decoder;

a comparator for comparing the data length information decoded by thedecoder with the data length counted by said counter; and

a controller for making such a judgement that the data is dropped out byway of said comparator when the data length information decoded by thedecoder is not coincident with the data length of the still picture datacounted by the counter, and for controlling said reader to again readout the same still image data.

Furthermore, according to the present invention, it is to provide adecoder comprising:

a memory controller for controlling read/write operations of stillpicture data from/into a memory, which has been reproduced from arecording medium on which the still picture data having at leastvariable data length and data length information corresponding to thestill picture data have been recorded;

a picture data length calculator for calculating a picture data lengthcorresponding to one screen based upon a starting address and an endaddress by detecting header information from said reproduced still imagedata;

a separator for separating picture information and variable length datafrom said reproduced still image data;

a comparator for comparing the variable length data separated by saidseparator with the picture data length calculated by said calculatingmeans; and

a generator for generating a variable length data error signal when saidcomparator Judges that the variable length data separated by theseparator is not coincident with the picture data length calculated bysaid calculator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram for explaining an XA format of aCD-ROM;

FIG. 2 is an explanatory diagram for explaining screen sizes of theNTSL/PAL systems;

FIG. 3A schematically indicates a structure of data recorded in the MPEGsystem;

FIG. 3B is a schematic diagram for representing a method for forming aP-picture;

FIG. 3C is a schematic diagram for representing a method for forming aB-picture;

FIG. 3D schematically indicates a sequence of a decoded data which hasbeen recorded in the MPEG system;

FIG. 3E is a schematic diagram for illustrating such a mode that thedata recorded in the MPEG system is encoded to b transmitted as a videodata stream;

FIG. 4A schematically indicates a structure of data recorded in unit ofa single program;

FIG. 4B shows a constructive ratio of the video data to the audio data,contained in the MPEG data having the above-explained data structure;

FIG. 5A is an explanatory diagram for indicating a basic structure of asector.

FIG. 5B schematically shows a structure of data when the above-describedsector is employed as the video sector;

FIG. 5C is an explanatory diagram for explaining a structure of datawhen the above-described sector is employed as the audio sector;

FIG. 6A is an explanatory diagram for indicating a recording format of aCD-DA disc;

FIG. 6B is an explanatory diagram for indicating a recording format of avideo CD disc;

FIG. 6C indicates a structure of data recorded at a program number 1 incase of the video CD disc;

FIG. 7 is an explanatory diagram for explaining a frame structure;

FIG. 8A is an explanatory diagram for showing subcode data;

FIG. 8B is an explanatory diagram for indicating a structure of sub-Qdata;

FIG. 9A is an explanatory diagram for explaining the sub-Q date in alead-in area;

FIG. 9B is an explanatory diagram for explaining the program and thesub-Q data in a lead-out area;

FIG. 10 is an explanatory diagram for indicating TOC data;

FIG. 11 is an explanatory diagram for showing a directory structure of avideo CD;

FIG. 12 is an explanatory diagram for explaining a PVD (principle volumedescripter) of a video CD;

FIG. 13 is an explanatory diagram for explaining an information area ofa video CD;

FIG. 14 is an explanatory diagram for explaining disc information in theinformation area of the video CD;

FIG. 15 is an explanatory diagram for showing a segment play itemcontent table in the disc information of the video CD;

FIG. 16 is an explanatory diagram for indicating a list ID offset tableof the video CD;

FIG. 17 is an explanatory diagram of showing a play list of the videoCD;

FIG. 18 is an explanatory diagram of indicating a play item number ofthe video CD;

FIG. 19 is an explanatory diagram of representing a section list of thevideo CD;

FIG. 20 is an explanatory diagram for indicating a list structure of thevideo CD;

FIG. 21 is an explanatory diagram for explaining a playback controloperation by the list structure of the video CD;

FIG. 22 is an outer view for showing a reproducing apparatus accordingto the present invention;

FIG. 23 is a schematic block diagram of the reproducing apparatusaccording to the present invention;

FIG. 24 is a schematic block diagram of an MPEG video decoder accordingto the present invention; and

FIG. 25 is a flow chart for indicating a process operation performedwhen a still picture is reproduced, according to the present invention.

DESCRIPTION OF THE INVENTION

Now, a description will be made of a reproducing apparatus capable ofreproducing video (picture)/audio information about a video CD and aCD-DA (digital audio CD and CD-G) as an embodiment of the presentinvention. As a video CD, there is a reproducing apparatus additionallyequipped with a playback control function. According to this embodiment,the first-mentioned reproducing apparatus may have such a playbackcontrol function.

The description will be made in accordance with the following sequence.

I. DATA STRUCTURE OF VIDEO CD

1. Data mode

a. video data,

b. audio data,

c. management data.

2. Track structure

3. Sector structure

4. Arrangement on disc

5. TOG and Subcode

6. Directory structure

7. Video CD data track

a. PVD (principle volume descriptor)

b. Video CD information

-b1- disc information,

-b2- entry table,

-b3- list ID offset table,

-b4- PSD (play sequence descriptor)

* play list,

* selection list,

* end list.

c. Segment play item

II. PLAYBACK CONTROL (PBC)

1. List structure,

2. Concrete example.

III. ARRANGEMENT OF REPRODUCING APPARATUS

1. Outer appearance,

2. Circuit block.

IV. OPERATION DURING REPRODUCTION OF STILL PICTURE

I. DATA STRUCTURE OF VIDEO CD

1. Data mode

A video CD standard is defined as follows. The MPEG (Moving PictureCoding Experts Group) system standardized as the high efficiency codingtechnique is utilized, and moving picture and audio data can bereproduced from a CD-ROM disc for longer than 60 minutes. As aconsequence, this video CD standard is useful as a home-use softwaresuch as music, movie pictures, and KARAOKE, and as an educationalsoftware, an electric publishing software, and a game software incombination with a still picture.

In this video CD, moving picture data is compressed based upon the MPEGsystem, and this moving picture data is multiplex on audio data forrecording purposes. Furthermore, the management data required for thereproducing operation is recorded on a preselected region.

In FIG. 1, there is indicated a format about data of a video CD (XAspecification).

a. Video Data

As apparent from FIG. 1, as a video recording format and an audiorecording format, 1.152 Mbits/sec is allocated to video data and 64Kbits/sec to 384 Kbits/sec are allocated to audio data. A pixel size(dimension) of the video data (moving picture) is given as follows:(352×240) pixels are allocated in the case of the NTSC (NationalTelevision System Committee) signal (29.97 Hz) and a film (23.976 Hz),whereas (52 ×288) pixels are allocated in the case of the PAL (PhaseAlternation by Line System) signal (25 Hz).

As a pixel number (quantity) of a still picture, (352×240) pixels areallocated in the case of the normal level of the NTSC system, and(704×480) pixels are allocated in the case of the high definition(precision) level of the NTSC system. (352×288) pixels are allocated inthe case of the normal level of the PAL system, and (704×576) pixels areallocated in the case of the high definition level of the PAL system.

The compressing/coding operation of video data (moving picture) iscarried out in accordance with the MPEG system as follows: Assuming nowthat a video (picture) signal before being compressed is of the NTSCsystem, a video signal is constructed of 30 frames per 1 second In thiscase of the NTSC system.

In accordance with the MPEG system, a video signal is subdivided into330 blocks (22 blocks in horizontal direction and 15 blocks in verticaldirection within 1 frame), data in each block is DCT (Discrete CosinedTransfer)-transferred, and the transferred data is re-quantatized toreduce a high frequency component thereof to zero so as to furtherreduce a total number of bits. Then, these blocks are rearranged toconstruct a rectangular shape in such a manner that the start blockthrough the end block are arranged in a zig-zag form within thisrectangular shape from the upper left corner of the 1 frame screen blockto the lower right corner thereof. A run length coding process isperformed so as to further compress a total number of bits.

With respect to the respective frames of the video signal compressed inthis manner, the video information about the temporally front and rearframes is very resemblance to each other. The information is furthercompressed by utilizing this feature, and three different sorts of videodata whose compression degrees are different from each other areprovided with respect to the video data of 1 frame.

These three sorts of video data are referred to an I-picture (IntraPicture), a P-picture (Predicted Picture), and a B-picture(Bi-directionally predicted Picture).

Then, generally speaking, as represented in FIG. 3A, with respect toeach of 30 frames for 1 second, an I-picture, a P-picture, and aB-picture are arranged.

In this case, for instance, the frames with 15 frame intervals are setas I-pictures I1 and I2, 8 frames of P-pictures P1 to P8 as well as 20frames of B-pictures B1 to B20 are arranged as shown in this drawing. Asection defined from a certain I-picture to a frame before the nextI-picture is referred to a GOP (Group of Picture).

As previously described, an I-picture corresponds to normal picture datacoded by the DCT transfer.

As indicated in FIG. 3B, a P-picture is produced by coding the closemost I-picture, or the close most P-picture with employment of movementcompensation. For instance, the P-picture P1 is formed based upon theI-picture I1, or the P-picture P2 is formed based on the P-picture P1.

Thus, the above-described P picture is such a further compressedpicture, as compared with the I-picture. It should be understood thatsince P-pictures are sequentially formed from the preceding I-picturesor P-pictures, when an error happens to occur in the previous P-picture,or the previous I-picture, this error would be propagated to the nextP-picture.

A B-picture is produced by employing either a past I-picture and afuture I-picture, or a past P-picture and a future P-picture, asrepresented in FIG. 3C.

For example, the B-pictures B1 and B2 are formed by using the I-pictureI1 and the P-picture P1, and the B-pictures B3 and B4 are formed byemploying the P-picture P1 and the P-picture P2.

A B-picture corresponds to the highly compressed data, as compared withthe compressed P-picture. Since this B-picture does not constitute adata forming reference, no error is propagated.

In accordance with the algorithm of the MPEG system, there is nospecific rule about a position and a synchronization of an I-picture ona recording medium, but these position and synchronization are allowedto be arbitrarily selected. This position/synchronization selection isdetermined based on various conditions of random access degrees andscene cutting. For example, when the random access degrees areespecially considered, as shown in FIG. 3A, at least two sets ofI-pictures are required within 1 second.

Moreover, it is possible to select presence degrees of the P-picture andthe I-picture within 1 frame. This selection is made by a memorycapacity of an encode means.

The encode means in the MPEG system rearranges the picture data streamto be outputted in order that the efficiency in the decoder isincreased.

For instance, in the case of FIG. 3A, the frame sequence to be displayed(decoder output sequence) is given by the frame number as shown in thelower portion of FIG. 3A. In order that the B-picture is recombined bythe decoder, the P-picture is required which is present before thisB-picture and constitutes a reference. As a result, on the encoder side,the frame sequence as shown in FIG. 3D is rearranged as indicated inFIG. 3E, and the rearranged pictures are transferred as a picture datastream.

b. Audio Data

The audio data format of the MPEG system corresponds to the codingspeeds from 32 Kbits/sec. to 448 Kbits/sec. in a wide range. It shouldbe understood that the coding speed of 224 Kbits/sec. is employed as tothe moving picture track after the track 2, taking account of an easysoftware magnification and a high sound quality. The sampling frequencyis selected to be 44.1 KHz similar to that of the CD-DA.

c. Management Data

Video data and audio data, and also management data used to performvarious controls of reproducing operations for these data are recordedon a video CD.

That is, similar to a CD-DA, a TOC (Table of Contents) and a subcode arerecorded on a video CD by which a program number and starting positions(absolute times) of the respective programs are indicated.

Furthermore, a program No. 1 is utilized as a video CD data track in avideo CD, and various sorts of management information is recorded on theabove-described program No. 1. Also, a playback control operation (willbe discussed later) is realized by employing the data appearing in thevideo CD data track of the above-described program No. 1.

These management data will be discussed later in detail.

2. Track Structure

Such a data structure of a program on which video data and audio dataare recorded where, for instance, a piece of music constitutes 1 programunit data is illustrated in FIG. 4A.

Similar to a CD-DA, assuming that a retrieve operation is carried outbased on a program number, a pause margin of 150 sectors is establishedat a head of 1 program.

Furthermore, 15 sectors subsequent to the pause margin are provided as afront margin, and final 15 sectors of a program are provided as a rearmargin, which are used as an empty data region.

A region between the above-described front margin and rear margin isused as an MPEG data region. As shown in FIG. 4B, both of sectors Vconstituting the video data and sectors A constituting the audio dataare time-divisionally multiplex to be recorded by way of theinterleaving manner in the MPEG data region in such a manner that aratio of the sectors V to the sector A is 6:1.

3. Sector Structure

A structure of a sector constituting a single data unit within a trackis represented n FIGS. 5A to 5C.

FIG. 5A indicates a basic structure of a sector.

1 sector is constructed of 2324 bytes of packs formed by a pack headerand pack data.

The 12-byte pack header is provided at a head portion of the sector, andthe remaining 2312 bytes are 1 packet.

In the pack header, there are provided, first, a 4-byte pack start code,and subsequently 5-byte system clock reference (SCR), and finally a3-byte MUX rate.

The system clock reference (SCR) corresponds to a code having a meaningof one sort of absolute time. Based upon this SCR as a reference, a PTS(Presentation Time Stamp:

Picture Output Starting Time) is determined (will be described later).

This SCR is expressed by SCR(i)=C+(i×1200). The symbol "i" indicates anindex number of a sector within a picture data stream. This index number"i" is selected to be "0" in the front margin portion of the head.Symbol "C" denotes a constant, i.e., is always "0". Numeral "1200" issuch a value (9000/75=1200) at a system clock of 90 Hz in a 75 Hzsector.

It should be noted that this pack header is provided in all of thesectors V of the video data.

While such a pack header is employed in a sector constructed by 1 pack,a 2312-byte packet subsequent to the pack header is so arranged as oneexample, as shown in FIG. 5B when the sector is used as the sector forrecording thereon the video data.

First, a packet header is provided at 18 bytes subsequent to the packheader.

3 bytes of the head portion of the packet header are used as a packetstart code. Then, 1 byte of ID, 2 bytes of a packet length, 2 bytes ofSTD (System Target Decoder), 5 bytes of PTS, and 5 bytes of DTS(Decoding Time Stamp) are recorded. The PTS corresponding to the pictureoutput start time is set so as to be synchronized with audio data. TheDTS indicates a decode start time.

2294 bytes subsequent to this packet header are allocated as a videopacket on which the video data is actually recorded. In other words, asexplained above, the picture data stream constructed of the I-pictureand the P-picture, and also the B-picture is recorded.

It should be noted that in the first video sector within such a sectionwhere the video sectors are continued, the video packet is defined as2294 bytes, as explained before, but the STD in the packet header may beomitted in the subsequent continued video sectors, and the video packetsmay be expanded to 2296 bytes.

In the case that a sector corresponds to such a sector capable ofrecording audio data, as an example, a 2312-byte packet subsequent tothe pack header is arranged as shown in FIG. 5C.

First, similar to the video sector, a packet header is providedsubsequent to the pack header. This packet header is arranged by a3-byte packet start code, a 1-byte ID, a 2-byte packet length, a 2-byteSTD, and a 5-byte PTS, namely 13 bytes.

Then, 2279 bytes are allocated as an audio packet, and compresseddigital audio data may be recorded on this audio packet. An empty areaof 20 bytes is additionally provided after this audio packet, so that 1pack (1 sector) of 2324 bytes is constructed.

The sector is arranged in the above-described manner. In this sector,time information for a synchronization purpose if SCR, DTS and PTS. Thatis to say, as illustrated in FIG. 4B, since the video sectors V and theaudio sectors A are time-sequentially arranged within 1 track, thesynchronization must be established among these sectors. The timeinformation of SCR, DTS, PTS is utilized to perform this synchronizationprocess.

In other words, while the time information SCR is employed as thereference clock, a time instant at which either the video packet, or theaudio packet is commenced to be decoded based on the DTS in therespective sectors. Furthermore, at the PTS, a time instant is indicatedwhen either the display is made, or the audio output is made.

As described above, the audio sector and the video sector are soarranged as to be mutually synchronized with each other based upon thesetime information.

4. Arrangement on Disc

Structures on a CD-DA disc and a video CD disc are shown in FIGS. 6A to6C.

As shown in FIG. 6A, in a CD-DA disc, a lead-in area is provided at aninnermost peripheral position of the disc, on which TOC data isrecorded. As the TOC data, start positions, program numbers, play timesand the like of the respective programs are recorded.

Subsequent to the lead-in area, program data are recorded as a program#1 to a program #n, and a lead-out area is provided at an outermostperipheral position. The digital audio data which has been quantized by16 bits at a sampling frequency of 44.1 KHz is recorded together withthe subcode data.

On the other hand, a structure on a video CD disc is indicated in FIG.6B.

Substantially similar to the CD-DA, also in the case of the video CD, alead-in area is provided at an innermost peripheral position of thisdisc, on which TOD data is recorded. Then, subsequent to the lead inarea, a program #1 to a program #n are recorded, and a lead-out area isprovided at an outermost peripheral position.

It should be noted that in the case of the video CD, the program #1 isnot used to record either the actual video data, or the actual audiodata as a first program, but is used as a video CD data track forrecording the management data.

Then, the actual video data, or the actual audio data is recorded on theprogram #2 to the program #n. In other words, as explained with respectto FIGS. 5B and 5C, the program #2 to the program #n are arranged by thevideo sectors and the audio sectors as shown in FIG. 4B.

Also, in the case of the video CD, a program on which only the audiodata has been recorded may be provided. In this case, similar to theCD-DA, the digital audio data quantized by 16 bits at the samplingfrequency of 44.1 KHz is recorded.

It should also be noted that the maximum program number of any of theCD-DA and the video CD is limited to 99. As a consequence, in the caseof the CD-DA, 99 pieces of program can be recorded at maximum, whereasin the case of the video CD, 98 sequences can be recorded at maximum. A"sequence" implies a single section of continued moving pictures. Forexample, when a picture such as KARAOKE is recorded, 1 piece of music (1program) corresponds to 1 sequence. When a movie is recorded, a singledisc normally corresponds to 1 sequence.

As represented in FIG. 6C, a PVD (principle volume descriptor), aKARAOKE basic information area, a video CD information area, a segmentplay item area, and other files (CD-I application programs etc) areprepared in the video CD data track with employment of the program #1.These areas will be explained later.

5. TOC and Subcode

A description now be made of the TOC and subcode recorded on a lead-inarea in a video CD and a CD-DA.

A minimum unit of data recorded on the video CD and the CD-DA becomes 1frame 98 frames constitute 1 block.

A structure of 1 frame is represented in FIG. 7.

1 frame is arranged by 588 bits, in which 24 bits at a head portion ofthis frame are allocated to sync data, and subsequent 14 bits areallocated to a subcode data area. Then, thereafter, data and a parityare arranged in the remaining frame portion.

The 98 frames having such a structure is arranged by 1 block, and thesubcode data derived from the 98 frames are combined with each other toform subcode data of 1 block as indicated in FIG. 8A.

The subcode data derived from the first and second frames (namely, frame98n+1, and frame 98n+2) provided at the head portion of the 98 framesare used as a sync pattern. Then, 96-bit channel data, namely thesubcode data of P, Q, R, S, T, U, V and W derived from the third frameto the 98th frame (frame 98n+3 to frame 98n+98).

Among them, the P channel and the Q channel are employed so as toperform the management purposes, e.g., access operations. It should benoted that the P channel merely indicates the pause portions between thesuccessive programs, and more precise controls are executed by the Qchannels (Q1 to Q96). The 96-bit Q channel data is constructed asindicated in FIG. 8B.

4 bits of the Q channels Q1 to Q4 are allocated to control data whichare used to identify, or discriminate the audio channel number, theemphasis operation, and the CD-ROM. That is, the 4-bit control data aredefined as follows:

[0 * * *]--2-channel audio,

[1 * * *]--4-channel audio,

[* 0 * *]--CD-DA,

[* 1 * *]--CD-ROM,

[* * 0 *]--digital copy not allowable,

[* * 1 *]--digital copy allowable,

[* * * 0]--no pre-emphasis,

[* * * 1]--pre-emphasis.

Note that symbol "*" indicates "don't care".

Next, 4 bits of the Q channels Q5 to Q8 are allocated to addresses whichare used as control bits of the sub-Q data.

When the 4-bit address becomes [0001], the sub-Q data of the subsequentQ channels Q9 to Q80 indicate audio Q data, whereas when the 4-bitaddress becomes [0100], the sub-Q data of the subsequent Q channels Q9to Q80 denote video Q data.

Then, the Q channels Q9 to Q80 are allocated to 72-bit sub-Q data, andthe remaining Q channels Q81 to Q96 are allocated to CRC.

In the lead-in area, the sub-Q data recorded thereon becomes the TOCinformation.

That is, the 72-bit sub-Q data of the Q channels Q9 to Q80 as to theQ-channel data read out from the lead-in area contain such aninformation as shown in FIG. 9A. Each of the sub-Q data contains 8-bitdata.

First, a track number is recorded. The track number is fixed to [00] inthe lead-in area.

Next, "POINT (point)" is described, and further, "MIN (minute)", "SEC(second)", and "FRAME (frame number)" are indicated as an elapse of timewithin a program.

Furthermore, "PMIN", "PSEC" and "PFRAME", are recorded. These "PMIN","PSEC" and "PRAME" are defined by the values of "POINT".

When the value of "POINT" is "01" to "99", these values imply theprogram numbers. In this case, as to these PMIN, PSEC, PFRAME, a programstart button (absolute time address) of this program number is recordedas a minute (PMIN), a second (PSEC), and a frame number (PFRAME).

When the value of POINT is "A0", the track number of the first programis recorded in the PMIN. The sorts of discs are defined by the value ofPSEC, for example, CD-DA, CD-I,and CD-ROM (XA specification).

When the value of POINT becomes "A1", the program number of the lastprogram is recorded on the PMIN.

When the value of POINT becomes "A2", a start point of the lead-out areais indicated as an absolute time address in PMIN, PSEC and PFRAME.

For instance, when 6 programs are recorded on the disc, as shown in FIG.10, data are recorded as the TOC by such sub-Q data.

As indicated in FIG. 10, all of the program numbers TNO are "00".

A block No. indicates one unit of sub-Q data which have been read as theblock data by the 98 frames, as explained before.

The same content of the respective TOC data is written over threeblocks.

As indicated in this drawing, when the POINT is "01" to "06", startpoints of the program #1 to the program #6 are indicated as PMIN, PSEC,and PFRAME.

Then, when the POINT becomes "A0", "01" is indicated as a first tracknumber in the PMIN. The sort of disc is discriminated based on the valueof the PSEC. When this disc is a CD-ROM (XA specification), asrepresented in the drawing, the PSEC="20". When this disc is a CD-DA,the PSEC="00". When this disc is a CD-I, the PSEC="10".

Then, the value of this POINT is recorded on a position of "A1", and thetrack number of the final program is recorded on the PMIN (in this case,track number is 6). The value of the POINT is shown at a position of"A2", and start points of the lead-out areas are indicated in the PMIN,PSEC, and PFRAME.

After the block n+27, the contents of the block n to the block n+26 areagain repeatedly recorded.

In the programs #1 to #n and the lead-out area, the sub-Q data recordedtherein contain information as shown in FIG. 9B.

First, a track number is recorded. That is, any one of "01" to "99" isrecorded in the respective programs #1 to #n. A program number in thelead-out area is "AA".

Subsequently, as an index, information capable of subdividing therespective programs is recorded.

Then, as an elapse of time within a program, there are indicated MIN(minute), SEC (second), and FRAME (frame number).

Furthermore, as AMIN, ASEC and AFRAME, absolute time addresses arerecorded as a minute (AMIN), a second (ASEC), and a frame number(AFRAME).

6. Directory Structure

A directory structure of a video CD is represented in FIG. 11.

In the video CD shown in FIG. 6B, as the directory structure, asindicated in FIG. 11, a video CD directory, an MPEG audio/video, aCD-DA, a segment, a CD-I, a KARAOKE, and a EXT are required.

The video CD directory is recorded in the video CD information areawithin the program #1 of FIG. 6B. Disc information, an entry table, alist ID offset table, and a play sequence descriptor are provided, whichwill then be discussed later.

The MPEG audio/video corresponds to namely audio/video sequence data. Inother words, in such a video CD capable of recording 99 tracks atmaximum, 98 pieces (maximum) of sequence data can be recorded from theprogram #2 to the program #99.

The segment is such segment play items #1 to #1980 by which 1980 unitscan be recorded at maximum. This is recorded in the segment play itemwithin the program #1.

Furthermore, in the CD-I application program within the program #1, thisdirectory file is assembled into the directory structure as the CD-I.When the KARAOKE basic information area is utilized, this directory fileis assembled as the KARAOKE into the directory structure.

When such a track on which only the audio data is recorded is employed,this directory file is assembled into the directory structure as theCD-Da. When the PSD-X.VCD and LOT-X.VCD are used, the directory filesthereof are assembled into the directory structure as the EXT.

7. Video CD Data Track

As previously explained, the program #1 is used as the video CD datatrack in the video CD.

As previously described with employment of FIG. 6C, there are providedthe PVD (principle volume descriptor), KARAOKE basic information area,video CD information area, segment play item area, and other files (CD-Iapplication program etc.).

As indicated in FIG. 6C, the PVD is arranged at a position on the discfrom an absolute time address of 00:02:16 (minute/second/frame).

The KARAOKE basic information area is arranged at a position on the discfrom the absolute time address of 00:02:16.

The video CD information area is arranged at a position on the disc froman absolute time address of 00:04:00.

Then, the segment play item area is arranged from a position indicatedin the video CD information area, and the CD-I application program isarranged from a position indicated in the PVD.

a. PVD (Principle Volume Description)

A structure of the PVD (principle volume descriptor) arranged at theposition on the disc from the absolute time address of 00:02:16 isrepresented in FIG. 12.

First, as a volume structure standard ID, data of "CD001" is recorded.Subsequently, a system identifier, a volume identifier, a volume numberof an album, and an album set sequence number are recorded. There aresome cases that either a single album is constructed of a single disc,or a single album is arranged by a plurality of discs. The volume numberof the album is equal to a total number of discs in a single album.Then, the album sequence number indicates which sequence of a disc inquestion is present within these discs.

Then, a logic block size, a bus total, an address of the bus table, anda route directory record are recorded.

Also, a disc title is recorded as the album identifier, and subsequentlyan issuer and a write name are recorded.

Furthermore, an application name of a CD-I is recorded as theapplication identifier.

Next, a copyright file name, an abstract file name, an index file name,a formation date, a correction date, an expiration date, an effectivedate, a file structure standard version number, and finally an XA labelcode are recorded.

b. Video CD Information

The video CD information is recorded at a position on the disc from theabsolute time address of 00:04:00.

As indicated in FIG. 13, as this video CD information, disc information,an entry table, a list ID offset table, and a play sequence descriptor(PSD) are provided. These may constitute the respective files in thevideo CD directory shown in FIG. 11.

The disc information is arranged at a position on the disc correspondingto the head position of the video CD information from the absolute timeaddress of 00:04:00.

The entry table is arranged at a position from an absolute time addressof 00:04:01.

The list ID offset table is arranged at positions defined from anabsolute time address of 00:04:02 to an absolute time address of00:04:33.

The play sequence descriptor (PSD) is arranged at a position from anabsolute time address of 00:04:34 up to an absolute time address of00:07:64 at maximum.

-b1- Disk Information

The disc information arranged from the absolute time address of 00:04:00will now be first explained.

A region of the disc information has such a structure as shown in FIG.14.

First, the system identifier of the video CD is recorded in the firstbyte to the eighth byte.

Subsequently, the version number is recorded in two bytes from the 9thbyte to the 10th byte. In case of the version 2.0, this version numberbecomes "$0200".

Then, the album identifiers specifically given to the respective discsare recorded in 16 bytes from the 11th byte to 26th byte.

The volume number in the album is recorded in 2 bytes from the 27th byteto the 28th byte, and the album set sequence number is recorded in thesubsequent 2 bytes. There are some cases that either a single album isconstructed of a single disc, or a single album is constructed of aplurality of discs. The volume number of the album becomes the discnumber in this single album. Then, the album set sequence numberindicates which sequence of the disc in question is present within thediscs.

A size map of a moving picture track is recorded in 13 bytes from the31st byte to the 43rd byte. This size map corresponds to data used todiscriminate that the data about the respective programs #2 to #99 arethe NTSC signal, or the PAL signal. In other words, an LSB (leastsignificant byte) of the first byte among the 13 bytes indicates theprogram #2, and the 1-bit data up to the program #99 are recorded untilthe bit 1 of the last byte. When the bit Corresponding to the respectiveprograms is equal to "0", this bit indicates the NTSC system. When thisbit is equal to "1", this bit indicates the PAL system.

The status flag is recorded in 1 byte at the 44th byte. In this 1 byte,a bit "0" is used as a flag of the KARAOKE basic information among thebit "0" to the bit "7".

When the bit "0" is equal to "0", there is no KARAOKE basic information.When the bit "0" is equal to "1", it is indicated that the KARAOKE basicinformation is recorded from the sector of the absolute time address of00:03:00.

A byte size of the PSD (play sequence descriptor) is indicated in 4bytes from the 45th byte to the 48th byte. As shown in FIG. 13, the PSDis recorded from the absolute time address of 00:04:34 to the absolutetime address of 00:07:64 at maximum. Since the byte size is variable,the byte size is indicated in the above-described 4 bytes.

As will be described later, the PSD is constructed as a plurality oflists (section list, play list, end list) used in the playback control,and the respective lists are recorded as the PSDs. It should be notedthat when there is no PSD, namely there is a disc having no playbackcontrol function, the above-described 4 bytes are set to "0".

The first segment address is indicated in 3 bytes from the 49th byte tothe 51st byte. As shown in FIG. 6C, it has been described that the startpoint of the segment item area is recorded in the video CD informationarea, and the above-described 3 bytes correspond to it.

As will be described later, with respect to the segment play item, 1980pieces of segment play items at maximum can be recorded in the segmentplay item shown in FIG. 6C. As the respective segment play items, thevideo data and the audio data, which are employed as the playbackcontrol are recorded.

The offset multiplier is recorded in 1 byte at the 52nd byte. This issuch a multiplier employed to calculate the address of the respectivelists in the PSD, and is fixed to "8" in this case.

The number of list ID is indicated in 2 bytes from the 53rd byte to the54th byte. This represents the quantity of effective ID recorded in alist ID offset table (will be discussed later).

The number of segment play item recorded in the segment play item areais indicated in 2 bytes from the 55th byte to the 56th byte.

The segment play item content table is recorded in 1980 bytes from the57th byte to the 2036th byte. This indicates attributes of therespective segment play items recorded in the segment item area.

That is, 1980 pieces of segment play items may be recorded as #1 to#1980 at maximum. As illustrated in FIG. 15, in this segment itemcontent table, the attribute data are recorded in correspondence withthe segment play items #1 to #1980 every 1 byte.

As to the respective bits (bit "0" to bit "7") of 1 byte, the attributedata are defined as follows: Note that the bit 6 and the bit 7 are notyet defined.

Bit 1, Bit 0=[00]--no MPEG audio data,

[01]--monophonic (monaural) audio data,

[10]--stereo audio data,

[11]--dual channel audio data.

Bit 4 to Bit 2:

[000]--no MPEG video data,

[001]--normal level still picture data in NTSC size,

[010]--high precision level still picture data in NTSC size,

[100]--unused,

[101]--normal level still picture data in PAL size,

[110]--normal/high precision level still picture data in PAL size,

[111]--moving picture data in PAL size.

Bit 5:

[0]--solo item, or head item of continuous items,

[1]--second item and subsequent items thereof among continuous items.

The disc information defined from the 2037th byte to the 2048th byte isundefined subsequent to such a segment play item content table.

-b2- Entry Table

As represented in FIG. 13, in the video CD information area, the entrytable is arranged from the absolute time address of 00:04:01.

In this entry table, a predetermined pint within either the audiosequence, or the video sequence may be entered as a starting point.

As a result, an ID corresponding to the entry file, a version number,and an entry number are recorded in this entry table 500 entries arerecorded as the actual entry points at maximum. In other words, theentries from #0 to #499 may be set.

A single entry is constructed of 4 bytes, and the track number isindicated by 1 byte among these 4 bytes, and also the sector address,i.e., ASEC, AMIN, AFRAME are indicated by the remaining 3 bytes.

-b3- List ID Offset Table

The list ID offset table is arranged in the sectors of the video CDinformation area from an absolute time address of 00:04:02 to anabsolute time address of 00:04:33.

A list ID is specifically attached to a play list and a selection list,which are recorded in a PSD (will be discussed later). In this list IDoffset table, an offset amount indicative of the position of each listin the PSD is indicated. Then, when a desired list to be reproduced isdesignated by a user, this video CD reproducing apparatus may grasp theposition of the designated list within the PSD with reference to thelist ID offset table, so that the content of the designated list can beexecuted.

As shown in FIG. 16, the list ID offset table is arranged by 32 sectorsat maximum, the offset amounts are indicated by each two bytes, and the64-kbyte offset is represented.

An area of PSD (will be discussed later) is defined from an absolutetime address of 00:04:34 to an absolute time address of 00:07:64 atmaximum, namely this PSD area becomes such an area of 3 seconds 31frames. This corresponds to 256 sectors 256 sectors correspond to 512Kbytes.

A value obtained by multiplying the offset value of 64 Kbytes by 8,which is represented in the list ID offset table, becomes 512 Kbytes.Numeral "8" corresponds to an offset multiplier at the 52nd byte of thedisc information shown in FIG. 14.

In other words, the offset becomes a numeral value for indicating apredetermined position in the PSD area as the byte position from the PSDhead position (position of offset "0000") by multiplying the offsetvalue by the offset multiplier "8" while 1 offset corresponds to 8bytes.

First, a start-up offset is recorded. This is fixed to a value of"$0000".

This FIG. 16 shows such a case that the number of list ID is 6, and therespective offset values as to the list ID1 to the list ID6.

It should be noted that as to the list ID1 arranged at the head of thePSD, the offset value is fixed to the value of "$0000".

Also, with respect to the unused list ID, the offset value is set to"$FFFF".

-b4- PSD (play sequence descriptor)

The PSD is provided at a position from an absolute time address of00:04:34.

In this PSD, a play list, a selection list, and an end list arerecorded. These lists are employed in a playback control (will bediscussed later), in which the data indicative of the content ofreproduction, and the hierarchical branch are recorded.

The play list does not contain data used to be branched to the lowerhierarchy (selection menu), and corresponds to a list for designating aseries of contents to be reproduced.

On the other hands, the selection list is such a list containing thedata used to be branched to the lower hierarchy (selection menu).

It should be noted that the list which should be first reproduced (playlist, or selection list) is the list ID1, and is recorded at a headposition (position of offset "00002) of the PSD.

* Play List

The play list for designating a series of contents to be reproduced isarranged as shown in FIG. 17.

First, a 1-byte play list header is provided and indicates that thislist corresponds to the play list.

Subsequently, as a number of item, the quantity of play items recordedin this play list is represented. The play item corresponds to such adata for indicating the content to be reproduced. The data fordesignating the play items are recorded in the play list as the playitem number #1 to the play item number #N.

The list ID specific to the respective lists is recorded in 2 bytessubsequent to the number of item.

Subsequently, a previous list offset, a next list offset, and a returnlist offset are each recorded in 2 bytes.

The previous list offset indicates a position (offset) of the list whichshould be advanced when the previous operation is performed. Forexample, when a position of a list located at an upper one stage isdesignated by the previous list offset, e.g., when the list is madehierarchical, the user can return to the operation condition by theprevious list by the previous operation.

When the previous list offset is equal to "$FFFF", it is prohibited toexecute the previous operation.

The next list offset indicates a position of a list which should becontinuously advanced either when the reproducing operation designatedby this play list is accomplished, or when the next operation isperformed.

The return list offset indicates a position of a list which should beadvanced when the return operation is performed. For example, when thelist is made hierarchical, if a position of a list located at thehighest stage is designated by the return list offset, then the user mayreturn to the operation condition by the list at the highest stage bycarrying out the return operation.

Next, a playing time of 2 bytes, a play item wait time of 1 byte, and anauto pause wait time of 1 byte are recorded.

The playing time indicates the number of sectors of the reproducingoperation based on this play list.

The play item wait time indicates a wait time when the reproducingoperation of each play item is ended. The wait times "0" to 2000 secondsare indicated by "$00" to "SEE". In case of "$FF", it implies thatuser's operation is waited.

The auto pause wait time indicates a wait time during the auto pauseoperation.

Finally, the numbers as to the play items #1 to #N to be reproduced areeach indicated by 2 bytes.

This play item number (PIN) is defined as indicated in FIG. 18.

When PIN="0", or "1", this play item is not reproduced.

When PIN="2" to "99", this PIN represents the track number. For example,when PIN="5", this play item becomes a play item for reproducing a track#5.

When PIN="100" to "599", this value (PIN-100) indicates the entry of theentry table. As previously described, the entry table may indicate 500entry points as the entries #0 to #499 at maximum. As the value(PIN-100) thereof, any of entry numbers #1 to #500 is designated.

When PIN="100" to "2927", the value (PIN-999) thereof represents thenumber of segment play item. In the segment play item area, 1980 piecesof segment play items may be recorded at maximum. As the value(PIN=999), any of segment play items #1 to #1980 is designated.

Both of PIN="600" to "999" and PIN="2980" to "$FFFF" are not defined.

For example, the three play items are recorded in the play list,assuming now that the play item #1 number was "04", the play item #2number was "1001", and the play item #3 number was "102".

Then, in the reproducing operation executed by this play list, the track#4 is first reproduced, subsequently the segment play item #2 isreproduced, and finally, the tracks by the entry #3 from the entry pointare reproduced.

* Selection List

The selection list is such a list to reproduce a selection menu so as tocause a user to select an operation to be processed. A structure of thisselection list is shown in FIG. 19.

First, a 1-byte selection list header is provided which indicates theselection list.

Subsequently, in an used 1 byte, a selection branch number in thisselection list is recorded. The maximum selection branch number is 99.

Next, the first number of the selection branch is indicated. This firstnumber is normally "1". However, when there are many selection branchesto be set and therefore a plurality of selection lists are employed, afirst selection branch number in the second, or subsequent selectionlist is Indicated.

Subsequently, list IDs specific to the respective lists are recorded by2 bytes.

Then, similar to the play list, a previous list offset, a next listoffset, and a return list offset are each recorded by 2 bytes.

In other words, the previous list offset indicates a position (offset)of a list along which the list should be advanced when the previousoperation is carried out. When the previous list offset is equal to"$FFFF", the previous operation is prohibited.

The next list offset indicates a position of a selection list whichshould be continuously advanced when the next operation is carried out.When there is no list continuously to be advanced, the next list offsetis set to "$FFFF".

Furthermore, the return list offset represents a position of a listwhich should be advanced when the return operation is performed.

For example, when it is so set that one selection is made by using aplurality of selection lists, these selection lists are effectivelyutilized. For example, when 12 selection branches are set and 4selection branches are set by the 3 selection lists respectively, therespective selection lists are continued along forward/backwarddirections by employing the previous list offset and the next listoffset, so that the user can search a desirable selection branch byperforming the previous operation/next operation.

Furthermore, a default list offset is recorded. This default list offsetindicates a position of a list, along which the list should be advancedwhen the user makes no selection, but performs the execution.

Also, a time out list offset is recorded. This time out list offsetindicates a position of a list, along which the list should be advancedwhen the user makes no input with respect to the selection menu underreproduction and a predetermined time has passed. When the time out listoffset is "$FFFF", no input is entered and a preselected time haselapsed. At this time, a specific selection branch is selected at randomfrom the selection branch indicated in the selection menu, and theprocess operation is advanced to this list.

Subsequently, a wait time until time out is recorded. When the wait timerecorded therein has elapsed while no input is made by the user, this isadvanced to the above-described time out list offset.

Next, a loop count and a jump timing are indicated. The loop countindicates the number of reproduction for repeatedly reproducing the playitem in this list. Also, the jump timing indicates a timing when thenext list is advanced after performing the selection operation.

Subsequently, a play item number (PIN) s indicated. This PIN indicates aplay item to be reproduced under execution condition of this selectionlist by a definition of FIG. 18. A thing to be reproduced in theselection list is the normal menu screen. As a consequence, as thesegment play item, the video data for the menu is recorded. There aremany cases that a specific segment play item in each of the selectionlists is designated.

For instance, when the menu image data corresponding to this selectionlist is recorded as the segment play item #4, the play item number (PIN)thereof becomes "1003".

As described above, a single PIN is provided in the selection list.

Finally, to indicate the operation to be actually executed by selectingthe desired selection branch, a selection #BSN offset to a selection#(BSN+NOS-1) offset are indicated by 2 bytes, respectively. It should benoted that symbol "BSN" is a first number of the selection branchrecorded in the 4th byte of the selection list, and symbol "NOS" is aselection branch number recorded in the 3rd byte of the selection list.As a consequence, in the selection list having the selection branches 1to 4, the selection #1 offset to the selection #4 offset are recorded.

Each of these selection offsets indicates a position of a list(selection list, or play list), along which the list should be advancedwhen this selection branch is selected.

For instance, when the user selects the selection branch 2 with respectthe menu display, it is designated that the process operation isadvanced to the list indicated by the selection #2 offset.

* End List

The end list represents a terminal of an application. The end list isarranged by 8 bytes, namely an end list header in 1 byte, and "$00" in 7bytes.

C. Segment Play Item

As shown in FIG. 6C, a segment play item area is provided in a video CDdata track. A start point of the segment play item area is indicated inthe disc information of FIG. 14 from the 49th byte to the 51st byte in 3bytes.

As a segment play item, 1980 pieces of segment play items may berecorded at maximum in the segment play item.

Each of these segment play items may be freely produced by the stillpicture data, the moving picture data, and the audio data.

A single segment is constructed of 150 sectors. The respective segmentplay item may be data reproduced as an independent item, or a pluralityof items continuously reproduced.

With reference to FIG. 15, each of these segment play items will now beexplain. In the disc information, the data attribute is indicated by thesegment play item content table recorded from the 57th byte to the2036th byte.

As previously explained, the menu screen of the section list may beprepared by using this segment play item.]

II. Playback Control (PBC)

1. List Structure

As described above, since the play list and the selection list areemployed, a so-termed "playback control (PBC)" may be realized in avideo CD. This playback control is a function to realize the PBC as asimple interactive type software with combination of a moving picture, astill picture and a voice in the video CD.

That is, the still picture data used to constitute several menu screensas the segment play item is prepared in the segment play item area. Thesegment play items can be branched to be reproduced by the selectionlist, and also the play item selected by the branching operation isreproduced in accordance with the play list.

In other words, a description file is formed which is made in thehierarchical form based upon the selection list and the play list. Inresponse to the selection made by the user, the process operation isadvanced to a lower hierarchical layer so as to thereby perform apredetermined reproducing operation.

As a basic list structure, the selection list is arranged at theuppermost position, and several play lists are arranged as the selectionbranches by this selection list. For example, specific play lists of theabove-explained selection list are designated as the selection #1 offsetto the selection #3 offset.

Then, the menu display is executed in the selection list so as to beselected by the user.

When the user selects, e.g., the selection #3, the process operation isadvanced to the play list indicated by the selection #3 offset, and thedata indicated as the play item #1 number to the play item #N number ofthis play list. For example, when the track #5 is designated as one playItem #1 number in the advanced play list, then the reproduction of thetrack 5 is executed.

2. Concrete Example

Referring now to FIG. 20 and FIG. 21, a concrete example of such aplayback control (PBC) operation will be explained. In this example, avideo CD is manufactured as a software of an English conversationlesson.

As indicated in FIG. 20, a list is recorded as a PSD from a position ofan absolute time address of 00:04:34 within the video CD informationarea.

In other words, selection lists S1, S2 and play lists P1 to P5 arerecorded.

To the respective lists, list IDs are attached as indicated in FIG. 21.That is, the list IDs are defined by such that a list ID of $0001 isattached to the selection list S1, a list ID of $0002 is attached to theselection list S2, a list ID of $0005 is given to the play list P1, alist ID of $0006 is given to the play list P2, a list ID of $0007 isattached to the play list P3, a list ID of $0003 is attached to the playlist P4, and a list ID of $0004 is attached to the play list P5.

When the process operation is entered into the playback controloperation, the selection list S1 whose list ID is equal to $0001 firstfunctions.

As the operations by the selection list S1, the reproduction is carriedout by the play item number (PIN) recorded therein.

A value of "1000" is indicated in this PIN. As easily understood fromFIG. 18, since this value of "1000" is equal to a numeral valueindicative of the segment play item #1, the segment play item #1recorded in the segment play item area is reproduced.

The reproduced output of this segment play item #1 becomes a stillpicture menu image (screen) used to select such an English lesson courseas indicated as PB1.

In the selection list S1, a selection #1 offset to a selection #1 offsetto a selection #3 offset, corresponding to the three selection branches,are recorded As a consequence, the three selection branches arerepresented by the reproduced output picture by the segment play item#1. It should be noted that symbol "Sel #N" indicates a selection #Noffset.

With regard to this picture PB1, the user enters a desirable selectionbranch number.

Assuming now that the selection branch number 1 is inputted by the user,the process operation is advanced to a list indicated in the selection#1 offset. The selection #1 offset is "#0004", and then "$0020" isobtained by multiplying this numeral value by an offset multiplier "8".This namely is equal to the offset byte of the selection list S2 withinPSD.

Then, a value of "1001" is indicated in the PIN within the selectionlist S2. That is, this value indicates the segment play item #2. As aresult, the segment play item #2 is reproduced.

A reproduced output PB6 of this segment play item #2 becomes a stillpicture menu image used to select the English lesson courses 1 through 3in the upper grade course.

To the contrary, assuming that the user inputs the selection branchnumber 1, the process operation is advanced to a list indicated in theselection #1 offset with the selection list S2. The selection #1 offsetis equal to "$0008", and then this numeral value is multiplied by theoffset multiplier "8", thereby obtaining "$0040". Namely, the processoperation is advanced to the play list P1.

In this play list P1, a value of PIN #1 is "2" and the track #2 isdesignated. Also, a value of PIN #2 is "3" and the track #3 isdesignated. Also, a value of PIN #2 is "3" and the track #3 isdesignated. As a consequence, when the process operation is advanced tothe play list P1, the track #2 is first reproduced to output a movingpicture (and also voice) PB7. This is used as the moving picture andvoice in the English lesson course 1 in the upper grade class.

When the reproducing operation of the track #2 is accomplished, thetrack #3 is subsequently reproduced to thereby output a moving picture(and voice) PBS.

On the other hand, if the user enters the selection branch number 3 atthe time when the menu picture PB6 is outputted by the selection listS2, then the process operation is advanced to the list indicated in theselection #2 offset within the selection list S2, namely the play listP2.

In this play list P2, the segment play item #3 is designated with thevalue "1002" of the PIN #1. As a consequence, when the process operationis advanced to the play list P2, the segment play item #3 is reproduced,so that for instance, a still picture (and voice) PB9 is outputted. Forinstance, the English lesson course 2 in the upper grade classcorresponds to such a lesson as a slide show.

If the user inputs the selection branch number 3 at the time when themenu picture PB6 is outputted by the selection list S2, then the processoperation is advanced to the list indicated in the selection #3 offsetwithin the selection list S2, namely the play list P3.

In this play list P3, a value of the PIN #1 is "8", and a track #8 isdesignated. It is assumed that this track #8 corresponds to such a trackhaving only digital audio data. Then, the track #8 is reproduced as theEnglish lesson course 3 in the upper grade class, so that the outputPB10 with only the voice is made.

Next, assuming now that the user inputs the selection branch number 2corresponding tot he middle grade class at the time when the menupicture PB1 is outputted based on the first selection list S1, theprocess operation is advanced to the list indicated by the selection #2offset In the selection list S1, namely a play list P4.

In this play list P4, a track #4 is designated with PIN #1=4, and also atrack #3 is designated with PIN #2=5. Accordingly, when the processoperation is advanced to the play list P4, the track #4 is firstreproduced to output a moving picture (and voice) PB2. Subsequently, thetrack #5 is reproduced to output a moving picture (and voice) PB3. Thisreproduce output is used as the moving picture and the voice belongingto the middle grade class.

Also, assuming that the user inputs the selection branch number 3corresponding to the beginner's grade class at the time when the menupicture PB1 is outputted based on the first selection list S1, theprocess operation is advanced to the list indicated by the selection #3offset in the selection list S1, namely a play list P5.

In this play list P5, a track #6 is designated with PIN #1=6, and also atrack #7 is designated with PIN #2=7. Accordingly, when the processoperation is advanced to the play list P5, the track #6 is firstreproduced to output the reproduced moving picture (and voice) PB4.Subsequently, the track #7 is reproduced to output the reproduced movingpicture and (voice) PB5.

This output is used as the moving picture and voice for the beginner'sgrade class.

As previously explained, it should be understood that the previous listoffset, the next list offset, and the return list offset may be recordedin the play lists and also the selection lists. Also, the default listoffset and the time out list offset may be additionally recorded in theselection list. As a consequence, the advance/backward operations of thelist may be performed in response to the operations.

When, for instance, "$0004" is recorded as the previous list offset ofthe play list P1, If the user carries out the previous operation duringthe operation of the play list P1, then the process operation isreturned to the selection list P2 where the

As previously explained, the video CD may be made in the simpleinteractive type software form by way of the playback control. With sucha function, the video CD may be widely applied not only to music andmovie, but also educational purposes, game purposes, and electronic bookpublishing purposes.

III. ARRANGEMENT OF REPRODUCING APPARATUS

1. Outer Appearance

A description will now be made of a reproducing apparatus capable ofreproducing the above-described video CD, according to an embodiment ofthe present invention.

The reproducing apparatus according to the embodiment may store therein5 sheets of video CDs and CD-DAs, which may be selectively reproduced,namely is a so-called "disc exchangeable video CD player".

An outer appearance of this reproducing apparatus is indicated in FIG.22.

Reference numeral 1 indicates a main body of a reproducing apparatus.

Reference numeral 2 denotes a disc loading unit provided on a frontpanel of the reproducing apparatus 1, from which a disc tray 30 shown inFIG. 23 is drawn to a front surface side. Five sheets of discs may beloaded on this disc tracy 30 in such a manner that these discs arearranged along the surface direction thereof. The discs are rotated in aroulette form, so that the disc to be reproduced is selected.

Reference numeral 3 represents a display unit constructed of a liquidcrystal display (LCD) panel. The LCD display panel 3 displays theoperation conditions, modes, number of selected disc, and operation timeof the reproducing apparatus.

Various sots of keys operated by a user are provided on this frontpanel. Reference numeral 4 indicates a power source ON/OFF key.

Reference numeral 5 denotes a reproducing key. This reproducing key 5also has a function of a selection key (selection enter key) used toperform the above-explained playback control operation.

Reference numeral 6 indicates a pause key, reference numeral 7represents a stop key, and reference numeral 8 shows an eject key.

Reference numeral 9 is a disc selection key. Five sets of disc selectionkeys "D1" to "D5" are prepared. These five disc selection keyscorrespond to five discs stored on the disc tray. For example, when thedisc selection key "D1" is depressed, the disc stored at the firststorage position on the disc tracy is loaded to a position of an opticalhead provided inside the reproducing apparatus so as to be reproduced.

Reference numerals 10 and 11 are keys for AMS (Auto Music Scan)operations. That is, reference numeral 10 indicates an AMS key to seek ahead portion having a smaller program number, whereas reference numeral11 denotes an AMS key to seek a head portion having a larger programnumber. Also, the backward head seeking key 10 owns a previous key usedto perform the previous operation during the above-explained playbackcontrol operation. Further, the forward head seeking key 11 owns a nextkey used to perform the next operation during the above-describedplayback control operation.

Reference numeral 12 shows a return key used to perform a returnoperation during the playback control operation.

Reference numeral 13 denotes a ± selection key used to perform aselection operation on a menu screen during the playback controloperation. In other words, the menu selection may be accomplished byselecting a desirable selection branch number by operating the ±selection key 13 from the menu screen, and by selectively operating thereproducing key 5 at the time when this desirable selection branchnumber is designated.

Reference numeral 14 is a disc skip key, and reference numeral 15 showsa disc change key.

Reference numerals 16 to 19 show selection keys for play modes, in whichreference numeral 16 is a normal reproducing mode key. When such a discadditionally equipped with the playback control function is reproduced,if the normal reproducing mode key 16 is depressed, then the reproducingapparatus is automatically entered into the playback control operation.

Reference numeral 17 denotes a shuffle mode key, and reference numeral18 indicates a program reproducing mode key.

Reference numeral 19 is a PBC off key by which the PBC mode is turnedOFF. When the PBC off key 19 is depressed while the disc having theplayback control function is loaded, the reproducing apparatus isbrought into the normal continuous reproducing operation from the menureproducing operation by the PBC mode.

Reference numeral 20 indicates a digest key, and reference numeral 21shows a digest mode key. A digest image (picture) about each of thestored discs may be displayed by operating the digest key 20. Byoperating the digest mode key 21, the digest image about the discadditionally equipped with the playback control function may beselectively used as the menu image, or the image in the track.

Reference numeral 22 is a bookmark register key, and reference numeral23 shows a bookmark reproducing key. During the reproducing operation,the user depresses the bookmark register key 22 to register thisreproducing point. Thereafter, the user depresses the bookmarkreproducing key 23 to reproduce from this point. For example, fivereproducing points may be designated to be registered on a single discby depressing the bookmark register key 22. After the bookmarkreproducing key 23 is depressed, when a selection is made of one ofthese registered bookmark points, the reproducing operation is commencedfrom this reproducing point. The registered bookmark point is selectedby employing, for example, the ± selection key 13 and the selection key5.

Reference numeral 24 denotes an infrared signal receiving unit. When aninfrared command signal is transmitted from a remote commander (notshown), this infrared command signal is received by this infrared signalreceiving unit 24 to be converted into an electric signal which willthen be acquired as operation information by an internal systemcontroller.

2. Circuit Block

FIG. 23 represents an internal circuit arrangement of the reproducingapparatus.

In FIG. 23, reference numeral 30 is a disc tray. Storage positions 301to 305 are provided on the disc tray 30, by which five discs can bemounted. Then, the disc tray 30 is so constructed as to be rotated by amotor 31. A certain storage position 30x is transferred to a position ofthe optical head 34 by this tray rotation. That is to say, the discmounted on this storage position 30x is loaded to the position of theoptical head 34. Reference numeral 32 shows a disc position sensor.Based upon the position of this disc position sensor 32, the systemcontroller 53 can grasp the present loading condition, namely whichstorage position 30x is located at the position of the optical head 34.

The loaded disc is chucked so as to be rotated by a spindle motor 33.Then, while this loaded disc is rotated by the spindle motor 33, thelaser light is illuminated from the optical head 34, and the reflectionlaser light from this disc is used to read out various information.

On the optical head 34, a laser diode functioning as a laser outputmeans, an optical system constructed of a deflection beam splitter andan objective lens, and a detector for detecting the reflection light aremounted. The objective lens 34a is held by a two-shaft mechanism 34b insuch a manner that this objective lens 34a is displacable along the discradial direction and the direction apart from the disc. Referencenumeral 35 indicates a thread mechanism for driving the optical head 34along the disc radial direction.

The information detected from the disc by the optical head during thereproducing operation is supplied to an RF amplifier 36. The RFamplifier 36 performs the calculation process of the suppliedinformation to thereby extract a reproduction RF signal, a trackingerror signal, a focusing error signal, and the like. Then, the extractedreproduction RF signal is supplied to a decoder unit 38 in which the EFMdemodulation (Eight Fourteen Demodulation) and the error correction areperformed. Also, P and Q channel subcode data are derived to be suppliedto the system controller 53.

The tracking error signal and the focusing error signal are supplied toa servo circuit 37. The servo circuit 37 produces various servo drivesignals based upon a tracking jump instruction, and an accessinstruction derived from the tracking error signal and the focusingerror signal, and also the rotation speed detection information of thespindle motor 33. Also, the servo circuit 37 controls the two-shaftmechanism 34b and the thread mechanism 35 to perform thefocusing/tracking control operations, and also controls the spindlemotor 33 in the CLV (constant linear velocity) mode.

Reference numeral 39 indicates a CD-ROM decoder. In the case that a discunder reproduction is a video disc, namely a so-called "CD-ROM formatteddisc", the decode process is carried out by the CD-ROM decoder 39 inaccordance with the CD-ROM format.

Among the signals decoded by the CD-ROM 39, the above-described variousdisc information such as the information about the playback control isacquired into the RAM 53a of the system controller 53.

Also, the audio data decoded by the CD-ROM decoder 39 is supplied to anMPEG audio decoder 40. The MPEG audio decoder 40 performs the decodingoperation at a preselected timing by using an audio RAM 41, and outputsa decoded audio signal.

Furthermore, the video data decoded by the CD-ROM 39 is furnished to anMPEG video decoder 4i. The MPEG video decoder 42 performs the decodingoperation at a predetermined timing with using a video RAM 43 andoutputs a decoded video signal (RGB outputs).

Reference numeral 44 is a switch unit switched in response to the sortof disc to be reproduced.

When the disc under reproduction corresponds to a CD-DA, the signalreproduced from this CD-DA is processed by the decoder unit 38 by way ofthe EFM demodulation and the CIRC (Cross Interleave Read-Solomon Coding)process, thereby producing a digital audio signal.

While the CD-DA is reproduced, the system controller 53 causes theswitch unit 44 to be connected to a terminal "t1". Accordingly, thedigital audio signal derived from the decoder unit 38 is converted intoan analog audio signal by a D/A converter 45, and this analog audiosignal is outputted to such an external appliance as an amplifiercircuit or an amplifier provided outside an audio output terminal 46.

When the disc under reproduction is an audio CD, the audio data isobtained from the MPEG audio decoder 40. During the reproduction of theaudio CD, the system controller 53 causes the switch unit 44 to beconnected to a terminal t2. As a result, the digital audio signalderived from the MPEG audio decoder 40 is converted by a D/A converter45 into an analog audio signal, and this analog audio signal isoutputted to such an external appliance as an amplifier circuit and anamplifier provided outside the audio output terminal 46.

When a video CD is reproduced, RGB video (picture) data is obtained asthe outputs from the MPEG video decoder 42. This RGB video data isconverted by a D/A converter 47 into an RGB analog signal. Then, the RGBanalog signal is supplied to an RGB/NTSC encoder 48 so as to beconverted into a composite video signal of the NTSC system. Thecomposite NTSC video signal is supplied to a terminal t2 of the switchunit 49.

During the reproduction operation of the video CD, the system controller35 causes the switch unit 49 to be connected to the terminal t2, so thatthe composite video signal of the NTSC system is supplied via an OSD(On-Screen Display) process unit 50 from a video output terminal 51 to amonitor apparatus and the like so as to output video information. Inresponse to an instruction issued from the system controller 53, the OSDprocess unit 50 operates to display a preselected superimpose image.

On the other hand, when the disc to be reproduced is a CD-DA and also isa CD-G, the still picture data are read out from the R to W channels ofthe subcodes. The still picture data is supplied to a CD-G decoder 52and then this still picture data is outputted as a composite picturesignal (still picture) of the NTSC system. During the reproduction ofthe CD-DA, the switch unit 49 is connected to the terminal t1, so thatthe picture signal reproduced from the CD-G is supplied via the OSDprocess unit 50 from the video output terminal 51 to the monitorapparatus and the like so as to output the video information. Also inthis case, the 0SD process unit 50 performs the predeterminedsuperimpose image display.

Reference numeral 54 shows a RAM used to back up the data of memories byway of a back-up power source 55. In this RAM 54, the data forregistering the bookmark point, i.e., such data which should not be lostwhen the power supply is turned OFF is stored. As apparently, an E-EPROMmay be employed.

Reference numeral 56 indicates an operation input unit for useroperations, and corresponds to the various operation keys (5 to 23) andthe infrared signal receiving unit 24 (and remote controller) shown inFIG. 22. When the disc is reproduced, the management informationrecorded on this disc, namely TOC and subcode data are read out, and aresupplied to the system controller 53. The system controller 53 causesthe display unit 3 to display the reproducing time and the like inaccordance with the management information.

FIG. 24 schematically represents an Internal arrangement of the MPEGvideo decoder 42. As represented in FIG. 23, the CD-ROM decoder 39, theMPEG audio decoder 40, the MPEG video decoder 42, and the systemcontroller 53 are connected via a bus B to each other. As this bus B,there are a data bus, a control bus, and an address bus as representedin FIG. 24. In the MPEG video decoder 42, the data input/outputoperations to these buses B are performed by a bus interface unit 81.

The video data outputted from the CD-ROM decoder 39, namely the MPEGvideo stream data corresponding to the compressed data read from thedisc is fetched from a bus interface unit 81 to a stream buffer 82.

The video data fetched by the stream buffer 82 is written via a RAMinterface unit 83 to a preselected region of a video RAM 43.

Reference numeral 84 shows a RAM controller for controlling an accessoperation to the video RAM 53, and the RAM controller 84 produces aread/write control signal and an address signal.

Reference numeral 85 indicates a variable length coding code processingunit corresponding to a unit for decoding the variable-length-coded databy the MPEG standard. In this variable length coding code processingunit 85, either the start code, or the end code contained in the bitstream is detected, and the various sorts of parameters are derived.

The compressed data which has been written from the stream buffer 82into the video RAM 43 and thereafter read out from the video RAM 43 isprocessed in the variable length coding code processing unit 85 toderive the header information of the respective layers. Also, the tablescorresponding to the respective variable length codes are selected to bedecoded. Furthermore, the run length code of the video data is decodedto reconstruct a block of a cosine (COS) coefficient.

Moreover, in the variable length coding code processing unit 85, avariable length coding code indicative an image data length of a singlescreen (1 macro block) is drawn from the compressed data stream. Then,the drawn variable length coding code is compared with an actual lengthof a single screen data stream, namely a data length defined from thestart code to the end code. If there is no coincidence, then a variablelength coding code error signal is produced.

When the data is correctly read out from the disc, the variable lengthcoding code should be coincident with the data length defined from thestart code to the encode. However, when a portion of data has beendropped out due to outer disturbance occurred while the data is readfrom the disc, the variable length coding code is not made coincidentwith the actual data length, namely the data length defined from thestart code to the end code.

As a consequence, such a case that the variable length coding code errorsignal is produced implies such a case that the data dropout happens tooccur. This variable length coding code error signal is supplied fromthe bus interface unit 81 via the control bus to the system controller53.

Reference numeral 86 indicates a dequantizing unit. The dequantizingunit 86 dequantizes the COS coefficient, and performs the multiplicationand the convolution process of the quantized coefficient in accordancewith the MPEG standard.

The output from the dequantizing unit 86 is supplied to an inverse DCTconverting unit 87. Since it is conceived that the output from thedequantizing unit 86 corresponds to the two-dimensional frequency, theinverse DCT converting unit 87 performs an inverse COS convertingcalculation so as to return this output from the dequantizing unit 86 tothe original image data.

Reference numeral 88 is a movement compensation processing unit. In theMPEG unit, the movement compensation frame prediction is employed whichis equal to the compression technique using correlation between thesuccessive frames. To the contrary, in this movement compensationprocessing unit 88, the data is read out from the video RAM 43 by usingthe movement vector contained in the bit stream, and then is calculatedwith the block data decoded from the dequantizing unit 86, thereby toreconstruct the image block.

The video data constituting one screen image reconstructed by thedecoding process is written into the video RAM 43.

The decoded video data are read from the video RAM 43 to be written intoa line buffer 89, and are further processed in an image processing unit90 based on various image processes such as interpolation/interleaveprocesses. Then, the resultant data are converted into RGB signals by amatrix circuit 91.

[IV. Operation performed When Still Picture Data is Reproduced]

A description will now be made of process operations by theabove-described reproducing apparatus when still picture data isreproduced.

As the still image reproducing operations, there are mainly the menu(image) screens shown in the PB1 and PB6 of FIG. 21, which is designatedby the selection list in the playback control, and the still image shownin the PB9, designated by the play list. In other words, the still imagedata as the segment play item recorded in the segment play item isreproduced.

As described above, there is such data containing only a moving pictureand voice as the segment play item. As to the attribute of therespective segment play item, a judgement can be made based on theinformation about the segment play item content table, as explained inFIG. 15.

When the segment play item is reproduced, the system controller 53executes a process operation indicated in FIG. 25.

In the case that a certain segment play item is reproduced by theplayback control or other operations, the system controller 53 Judgesthe attribute of the segment play item to be reproduced from the segmentplay item content table, and stores this judgement information into theRAM 53a.

Then, at the time when this segment play item data reading operation isaccomplished, the system controller 53 judges whether this read datacorresponds to the still picture data, or the moving picture data basedupon the information stored in the RAM 53a (S101). When this read datais the moving picture data, the process operation is ended under normalcondition.

To the contrary, when the read data corresponds to the still picturedata, the process operation is advanced to a step S102 at which avariable "n" is set to 1.

Next, a check is done as to whether or not the sector address decoded bythe CD-ROM decoder 39 while this segment play item data is read out iscorrectly continued (S103). When the continuity of the sector address isnot maintained, it may be such a case that the data portion in sectorunit is dropped out from the read data. In this data to dropout case,since the segment play item data is not correctly carried out, theprocess operation is not accomplished under normal condition, but isadvanced to a step S106.

Conversely, when the continuity of the sector address is maintained, aconfirmation is made as to whether or not the variable length codingcode error signal is produced (S104). As previously explained, such acase when the variable length coding code is not coincident with theactually read data length, i.e., the data length defined from the startcode to the end code corresponds to a case when a data portion hasdropped out. Then, the variable length coding code error signal issupplied from the variable length coding code processing unit 85 issupplied to the system controller 53. When this variable length codingcode error signal is issued, since the segment play item data cannot becorrectly performed, the process operation is not accomplished undernormal condition, but is advanced to a step S106.

When no variable length coding code error signal is issued, a judgementis done as to whether or not the end code can be correctly detected(S105). If the end code is correctly detected, then the processoperation is accomplished under normal condition. Conversely, when theend code could not be correctly detected, since the screen display maynot be correctly performed, the process operation is not accomplishedunder normal condition, but is advanced to a step S106.

Such a case that the process operation is not accomplished under normalcondition, but is advanced to the step S106, corresponds to a case whenthe screen display could not be correctly performed in the monitorapparatus due to the dropout of read data. Therefore, a confirmation ismade as to whether or not the variable "n" is equal to 16. When thevariable "n" is not equal to 16, this variable "n" is incremented(S107).

Then, at a step 108, the segment play item for constituting this stillimage data is again accessed to the optical head 34, and the data isagain read from the disc.

Then, when the data reading operation is complete, the judgementsdefined at the steps S103, S104 and S105 are carried out. When no datadropout occurs, the process operation is accomplished under normalcondition. In other words, when the still image data without any dropoutcan be obtained by again performing the data reading operation, so thatthe normal screen display is made on the monitor apparatus.

When a data portion again happens to occur, the process operationsdefined after the step S106 are repeated.

It should be noted that when n=16, namely the data reading errors arecontinuously produced 16 times, the process operation is accomplished asan erroneous operation.

In the case that a disc has a scratch noise, for instance, data cannotbe properly read. In such a case, if there is no limitation in the datareading time, then the process operation is repeatedly performed forever. It should be noted that the reading time restriction is notlimited to 16.

As previously described, the data dropout may be judged by monitoringthe variable length coding code error signal and also the continuity ofthe sector address. When the data dropout happens to occur, the datareading operation is immediately performed. Therefore, it can be avoidedthat the unproper still picture is displayed on the monitor.

For example, such a condition can be avoided that no menu screen portionindicative of the selection branch is displayed and thus, the usercannot perform the selection operation on the selection branch.

What is claimed:
 1. A reproducing apparatus for reproducing a recordingmedium on which both of still picture data having at least variable datalength, and data length information corresponding to the still picturedata have been recorded, comprising:reading means for reading out bothsaid still picture data and said data length information correspondingto the still picture data from the recording medium; decoding means fordecoding the still picture data and also the data length informationcorresponding to said still picture data, which are read out by saidreading means; measuring means for measuring a data length of said stillpicture data decoded by said decoding means; comparing means forcomparing the data length information decoded by the decoding means withthe data length measured by said measuring means; and controlling meansfor making such a judgement that the still picture data is dropped outby way of said comparing means when the data length information decodedby the decoding means is not coincident with the data length of thestill picture data measured by the measuring means, and for controllingsaid reading means to again read out the same still picture data.
 2. Areproducing apparatus as claimed in claim 1, further comprising addressdata judging means for judging a continuity of an address of saiddecoded still picture data, wherein:when said address data judging meansjudges that the address is discontinuous, said controlling meanscontrols said reading means to again read the same still picture data.3. A reproducing apparatus as claimed in claim 1, further comprising:enddata judging means for judging as to whether or not an end code of saiddecoded still picture data can be detected, wherein:when said end datajudging means cannot detect the end code of the decoded still picturedata, said controlling means controls said reading means to again readthe same still picture data.
 4. A reproducing apparatus as claimed inclaim 2, further comprising:end data judging means for judging as towhether or not an end code of said decoded still picture data can bedetected, wherein:when said end data judging means cannot detect the endcode of the decoded still picture data, said controlling means controlssaid reading means to again read the same still picture data.
 5. Areproducing apparatus for reproducing a recording medium on which bothof still picture data having at least variable data length, and datalength information corresponding to the still picture data have beenrecorded, comprising:a reader for reading out both said still picturedata and said data length information corresponding to the still picturedata from the recording medium; a decoder for decoding the still picturedata and also the data length information corresponding to said stillpicture data, which are read out by said reader; a counter for countinga data length of said still picture data decoded by said decoder; acomparator for comparing the data length information decoded by thedecoder with the data length counted by said counter; and a controllerfor making such a judgement that the still picture data is dropped outby way of said comparator when the data length information decoded bythe decoder is not coincident with the data length of the still picturedata counted by the counter, and for controlling said reader to againread out the same still picture data.
 6. A reproducing apparatus asclaimed in claim 5, further comprising:an address data judger forjudging a continuity of an address of the still picture data decoded bysaid decoder, wherein:when said address data judger judges that theaddress is discontinuous, said controller controls said reader to againread the same still picture data.
 7. A reproducing apparatus as claimedin claim 5, further comprising:an end data discriminator for judging asto whether or not an end code of said decoded still picture data can bedetected; wherein:when said end data discriminator cannot detect the endcode of the decoded still picture data, said controller controls saidreader to again read the same still picture data.
 8. A reproducingapparatus as claimed in claim 6, further comprising:an end datadiscriminator for judging as to whether or not an end code of saiddecoded still picture data can be detected; wherein:when said end datadiscriminator cannot detect the end code of the decoded still picturedata, said controller controls said reader to again read the same stillpicture data.
 9. A method for reproducing still image data from arecording medium on which both still picture data having at leastvariable data length, and data length information corresponding to thestill picture data have been recorded, comprising:a step for reading outboth said still picture data and said data length informationcorresponding to the still picture data from the recording medium; astep for decoding the still picture data and also the data lengthinformation corresponding to said still picture data, which are read outby said reading step; a step for measuring a data length of said stillpicture data decoded by said decoding step; a step for comparing thedecoded data length information with the measured data length; and astep for making such a judgment that the still picture data is droppedout by way of said comparing step when the decoded data lengthinformation is not coincident with the measure data length of the stillpicture data, and for again reading out the same still picture data. 10.A reproducing method as claimed in claim 9, further comprising:a stepfor judging as to a continuity of an address of the decoded stillpicture data; wherein:when said judging step judges that the address isdiscontinuous, a control is made to again read the same still picturedata.
 11. A reproducing method as claimed in claim 9, furthercomprising:a step for judging as to whether or not an end code of thedecoded still picture data can be detected; wherein:when the end code ofsaid decoded still picture data cannot be detected at said step, acontrol is made to again read the same still picture data.
 12. Areproducing method as claimed in claim 10, further comprising:a step forjudging as to whether or not an end code of the decoded still picturedata can be detected; wherein:when the end code of said decoded stillpicture data cannot be detected, a control is made to again read thesame still picture data.
 13. A decode circuit comprising:controllingmeans for controlling read/write operations of still picture datafrom/into storage means, which still picture data has been reproducedfrom a recording medium on which the still picture data having at leastvariable data length and data length information corresponding to thestill picture data have been recorded; picture data length calculatingmeans for calculating a picture data length corresponding to one screenbased upon a starting address and an end address by detecting headerinformation from said reproduced still picture data; separating meansfor separating picture information and data length information from saidreproduced still picture data; comparing means for comparing the datalength information separated by said separating means with the picturedata length calculated by said calculating means; and generating meansfor generating a variable length data error signal when said comparingmeans judges that the data length information separated by theseparating means is not coincident with the picture data lengthcalculated by said calculating means.